1. Field of the Invention
The invention pertains to counterbalanced movable or removable closures, more particularly to an interlocking jamb mounted locking shoe and sash mounted locking pivoted support arm system.
2. Description of the Prior Art
U.S. Pat. No. 2,796,630 patented Jun. 25, 1957 by G. B. Haas describes a self-locking sash balance in which a plunger from the sash rests upon a first radial side of a tripping lever that is pivotally mounted on a shoe that is biased upward by a balance spring. The second radial side of the tripping lever engages a pivoted detent so that when the plunger applies weight of the sash upon the first radial side, the second radial side presses upward on one side of the detent, rotating the other side of the detent out of biting engagement with a vertical side of the track in which the shoe rides.
U.S. Pat. No. 4,799,333 patented Jan. 24, 1989 by Westfall et al. describes a lock shoe system for a take-out window in which a horizontal pin from the sash pushes back a biter knife lever pivotally mounted on the balance shoe so that the knife disengages from the vertical track in which the shoe slides.
U.S. Pat. No. 5,189,838 patented Mar. 2, 1993 by N. R. Westfall describes a tilt sash lock shoe system in which an elongated sash pin can be lowered into or lifted vertically from a slot formed by confronting first and second vertical surfaces. The first vertical surface is a wall of the shoe. The second vertical surface is on a pivoted element that has a biting edge on one side of the pivoted element, that is rotated against the window track by upward force of the system's counter balance spring on the other side of the pivoted element. When the sash is tilted from the vertical with the pin in the shoe, or when the sash is removed from the window, the biting edge presses into the track. When the sash is vertical with an oblong end of the pin in the shoe, the oblong end forces the first and second vertical surfaces apart which rotates the pivoted element so that the biting edge is moved away from the track.
U.S. Pat. No. 5,231,795, patented Aug. 3, 1993 by N. R. Westfall describes a shoe designed to be supported by a spring counterbalance system, that is mounted on a jamb for vertical movement on the jamb. A lower outward corner of a sash rests on an inward extending platform extension of the shoe. A horizontally sliding bolt in the shoe is moved inward horizontally into a recess in the lower corner of the sash. Movement of the bolt is by a vertical pin eccentrically mounted on the top of a cylinder that rotates on a vertical axis. The cylinder is turned by a hex keyed hand tool from below the cylinder. In order to remove the sash from the window, the sash is moved down until an upward turned outer end of the bolt is below a downward depending lance that extends outward from the jamb in the direction of the sash. The bolt is slid outward so that when the sash is lifted, the shoe moves up until the outer end of the bolt catches under the lance. The sash, now free of the bolt, is then slid laterally off the platform for removal from the window frame.
U.S. Pat. No. 6,041,475 patented Mar. 28, 2000 by M. J. Nidelkoff for a locking counterbalance shoe for tiltably removable sash windows describes a balance shoe in which a first element that is supported by the balance spring contains a second pivoted locking element having a serrated edge that grips the jamb track under the urging of an actuator spring between the first and second elements when there is no sash in the window frame. The second element unlocks from the jamb track when the flat sash pin of a vertical sash rests upon the second element, compressing the actuator spring. When the sash is rotated from vertical, the flat sash pin turns the second element to the locking position wherein the serrated edge grips the jamb track.